Why does Heart rate increases while oxygen levels drop during movement?

During movement, the body's demand for oxygen increases to support heightened physical activity, leading to a rise in heart rate. As muscles work harder, they consume more oxygen, causing blood oxygen levels to drop. In response, the heart pumps faster to deliver more oxygen-rich blood to the tissues, compensating for the decreased oxygen availability. This physiological response ensures that the body maintains an adequate supply of oxygen to sustain energy levels during exercise.